Flares are pyrotechnic devices designed to emit intense electromagnetic radiation at wavelengths in the visible region (i.e., light), the infrared region (i.e., heat), or both, of the electromagnetic radiation spectrum without exploding or producing an explosion. Conventionally, flares have been used for signaling, illumination, and defensive countermeasures in both civilian and military applications.
Flares produce their electromagnetic radiation through the combustion of a primary pyrotechnic material that is conventionally referred to as the “grain” of the flare. The grain conventionally includes magnesium and fluoropolymer-based materials. Adding additional metals or other elements to the primary pyrotechnic material may alter the peak emission wavelength emitted by the flare.
Decoy flares are one particular type of flare used in military applications for defensive countermeasures. Decoy flares emit intense electromagnetic radiation at wavelengths in the infrared region of the electromagnetic radiation spectrum and are designed to mimic the emission spectrum of the exhaust of a jet engine on an aircraft.
Many conventional anti-aircraft heat-seeking missiles are designed to track and follow an aircraft by detecting the infrared radiation emitted from the jet engine or engines of the aircraft. As a defensive countermeasure, decoy flares are launched from an aircraft being pursued by a heat-seeking missile. When an aircraft detects that a heat-seeking missile is in pursuit of the aircraft, one or more decoy flares may be launched from the aircraft. The heat-seeking missile may, thus, be “decoyed” into tracking and following the decoy flare instead of the aircraft.
Conventional decoy flares include an elongated, generally cylindrical grain that is inserted into a casing. The casing may have a first, aft end from which the decoy flare is ignited and a second, opposite forward end from which the grain is projected upon ignition. The generally cylindrical grain can include grooves or other features that extend longitudinally along the exterior surface thereof to increase the overall surface area of the grain.
The ignition system of a decoy flare conventionally includes an impulse charge device positioned within the casing adjacent the aft end thereof, and a piston-like member positioned between the impulse charge device and the grain. The ignition system may further include a first igniter material positioned on the side of the piston-like member adjacent the impulse charge device, and a second igniter material on the side of the piston-like member adjacent the grain. This second igniter material (often referred to as “first-fire” material) may surround the grain and may be disposed within the longitudinally extending grooves of the grain.
The impulse charge device may be ignited by, for example, an electrical signal. Upon ignition, the impulse charge device may explode or cause an explosion. The expanding gasses generated by the explosion force the piston-like member and the grain out from the second end of the casing, and the explosion may further substantially simultaneously ignite combustion of the first ignition material. The piston-like member may include a mechanism that causes or allows the first igniter material to ignite combustion of the second igniter material after the piston-like member and the grain have been deployed from the casing by the impulse charge device. The combustion of the second igniter material ignites combustion of the grain itself.
By increasing the surface area of the grain, the surface area of the interface between the second igniter material (i.e., first-fire material) and the grain may be increased, enhancing the efficiency by which the second igniter material ignites combustion of the grain.
Conventional igniter materials used as the second igniter material (i.e., first-fire material) in decoy flares conventionally include combustible powders, slurries, and sol-gel compositions.
Flares are extremely dangerous and the ability to safely fabricate and use flares is a constant challenge to those working in the art. Furthermore, the incorporation of safety features or elements into flare designs has, in some cases, detrimentally affected the reliability of the decoys and caused an increase in the number of decoys that fail to properly and fully ignite. There is an ongoing need in the art for flares that are easier and safer to fabricate and that have increased ignition reliability.